Just changed spark plugs and spark plug wires on my '96 t100 with the 5vz-fe engine and it started idling and running rough. Once the engine is hot, it idles fine. I made sure the wires were connected properly and running to the right cylinders. I made sure the gap between the 2 electrodes on the plugs was the specified 0.043. There was some oil on the plug in cylinder 4 (not the inside with the electrode, but the other side of the seal) but that doesn't seem like too big a deal based on this thread. Any thoughts or suggestions?

 

Did you put the correct plugs in? 3.4 motors do not use the standard plug that has been around for years, the one that has the little curve at the end of the plug.

There is a sticker on the front of the motor, white with blue drawing if I recall right, saying not to use the common plug.

I only know the engines by 22,3.0 or 3.4 so I may be wrong on your information. Just to be on the safe side get your plugs from the dealer for your truck. The wrong plug in a 3.4 will make an effect on it. If it was running fine before you changed plugs, I feel it is something you did incorrectly and should be an easy fix.

 

So it wasn't running perfectly before (throwing a cylinder 5 misfire code), but is definitely running worse now. I used the plugs that the manual specified; the non-standard dual electrode ones. Funny thing is that I pulled out the "standard plug" that you referred to from the engine, meaning the last person to replace the plugs used the wrong ones.

From what I read, it seems to be a matter of putting all original plugs back in and replacing them one by one with the new ones to see if there was a bad plug in the batch.